The present invention relates to digital communication apparatus and in particular to the apparatus of a modulator driver for driving modulators of digital electro-optical fiber communication systems.
High speed digital and optical communication systems are widely installed in many areas of the United States. These types of communication systems generally have transmitter/receiver apparatus and a transmission facility or line interconnecting the transmitter/receiver apparatus to provide a path over which data may be exchanged between the transmitter/receiver apparatus. Increasing advances in technology and the need for more information require greater speed in the rate of transmitting data. The technology has went from analog systems to digital information systems capable of transmitting digital information in the form of logical xe2x80x9c0xe2x80x2sxe2x80x9d and xe2x80x9c1xe2x80x2sxe2x80x9d oftentimes referred to as bits. In an effort to increase the speed of transmission systems, the technology has advanced to the use of optical transmission systems using optical transmitter/receivers interconnected by optical transmission facilities such as optical fibers that transmit optical pulse bit information between the optical transmitter/receivers.
Digital transmitters and receivers are oftentimes connected by long transmission facilities. Typically, a digital transmitter applies binary digital signal information to the transmission facility which is then sent to the receiver which is designed to receive and decode data contained within the received information. The characteristics of the transmission line often times deforms the waveform format of the transmitted information such that the transmitted information is meaningless when it is received by the distant receiver. Thus, long optical fiber transmission lines oftentimes have regenerator or repeater units that connect the output end of an incoming transmission line through the regenerator or repeater units to the input end of an output transmission line. The regenerator or repeater units operate to regenerate the incoming transmission line information and apply the regenerated transmission line information to the outgoing transmission line. At the originating end a transmitter will receive data and modulate the data into optical data which is applied as transmission information to an outgoing transmission line connected to the transmitter. A receiver connected to the output of an incoming transmission line decodes the received transmission line information back into the data.
The transmitters, regenerator or repeater units and the receivers have modulators which function to convert data into optical transmitted transmission line information and the received optical transmission line information into data. Modulator driver (MDR) units are used in these units to control the modulators to provide these conversions. Present modulator driver apparatus have several single compression-limiting amplifiers connected in series to allow the modulator drivers to achieve fast rise and fall times. However, these types of apparatus have poorly controlled performance over necessary input and output range of signals and suffer poorly controlled overshoot, undershoot and eye opening operation. A problem arises in that in providing high speed transmission of data on these systems it is necessary to have a minimal bit error rate and to maximize the extinction ratio of optical data. Additionally, it is very important to minimize the power consumption of the modulator driver unit driving the modulator in that low power is necessary for high density wave division multiplexed applications.
It is an object of the invention to provide processor controlled low power modular driver apparatus for driving a modulator to receive multiplexed binary data signals and generate high fidelity variable gain output signals with a low level of over and undershoot and with a high extinction ratio for driving the modulator to modulate a light wave in high density wave division multiplexed applications.
It is also an object of the invention to provide processor controlled low power modular driver apparatus having limited amplifier apparatus for receiving multiplexed binary data signals and generating amplified and limited frequency output signals representative of the received multiplexed binary data signals.
It is also an object of the invention to provide processor controlled low power modular driver apparatus having differential amplifier apparatus connected to an output of limited amplifier apparatus for precisely controlling the amplitude and generating a low level of over and undershoot of output signals over a wide range of the limited amplifier output signals in response to limited frequency output signals generated by the limited amplifier apparatus.
It is also an object of the invention to provide processor controlled low power modular driver apparatus having processor controlled linear amplifier apparatus connected to limited and differential amplifier apparatus for generating high fidelity output signals with low over and undershoot and with a high extinction ratio for driving a modulator to modulate a light wave in optical high density wave division multiplexed applications.
In a preferred embodiment of the invention, apparatus for driving a modulator to modulate a light wave in optical high density wave division multiplexed applications has a processor controlled modulator driver for receiving multiplexed binary data signals and generating high fidelity variable gain output signals with a low level of over and undershoot and having a high extinction ratio in response to receipt of the multiplexed binary data signals for driving the modulator to modulate the light wave.
Also in accordance with the preferred embodiment of the invention, apparatus for driving a modulator for modulating data signals onto a light wave has a limited amplifier for receiving multiplexed binary data signals and for generating amplified and limited frequency output signals representative of the received multiplexed binary data signals. The modulator driver apparatus also has a differential amplifier connected to an output of the limited amplifier for precisely controlling the amplitude and generating a low level of over and undershoot of output signals over a wide range of the limited amplifier output signals. Processor controlled linear amplifier means connected to the output of the differential amplifier generates high fidelity output signals with low over and undershoot and a high extinction ratio for driving the modulator.
Also in accordance with the preferred embodiment of the invention, apparatus for driving a modulator to modulate multiplexed binary data signals onto a light wave has a programmed processor for controlling operation of the modulator driving apparatus and a limited amplifier for receiving the multiplexed binary data signals and generating amplified and limited frequency output signals representative of the received multiplexed binary data signals. The modulator apparatus also has a differential amplifier connected to an output of the limited amplifier and controlled by the processor for precisely controlling amplitudes and generating a low level of over and undershoot of output signals over a wide range of the limited amplifier generated limited frequency output signals. A pair of linear amplifiers connected in series to the output of the differential amplifier generates high fidelity output signals with low over and undershoot and a high extinction ratio for driving the modulator. Controller apparatus connected to the differential amplifier and responsive to the processor selectively controls amplitudes of the differential amplifier output signals. A plurality of programmable resistor arrays controlled by the controller in response to instructions generated by the processor supplies power to the linear amplifiers to equalize gains thereof and a peak detector connected to the output of the linear amplifiers detect an absence of linear amplifier generated signals as a loss of signals for modulating the modulator.